Removable plug arrangement and method of removing a plug arrangement

ABSTRACT

A removable plug arrangement includes at least one plug configured to lead or follow a hardenable material that is pumped through a tubular, the plug has one or more portions made of a material configured to weaken when exposed to an activation fluid.

BACKGROUND

Cementing of a liner or a casing in a well is done to, among otherthings, prevent flow in an annular space between the liner or casing andthe open borehole. It is common to perform several cementing operationswithin a single deep well. When additional drilling is required after acementing operation has been completed, the cementing plugs, shoe andcement located at the bottom of the section of well just cemented needto be drilled through before the drill bit can begin drilling into theearth formation again. Drilling through a plug can damage or dull adrill bit, can generate undesirable debris within the wellbore and candelay drilling progress in the earth formation. Systems and methods thatalleviate the foregoing concerns are well received in the industry.

BRIEF DESCRIPTION

Disclosed herein is a removable plug arrangement. The arrangementincludes at least one plug configured to lead or follow a hardenablematerial that is pumped through a tubular, the plug has one or moreportions made of a material configured to weaken when exposed to anactivation fluid.

Further disclosed herein is a method of removing a plug arrangement. Themethod includes exposing one or more portions of at least one cementingplug to an activation fluid capable of weakening the one or moreportions, weakening the one or more portions, and drilling or millingthrough the weakened one or more portions.

Further disclosed herein is a removable plug arrangement. Thearrangement includes a volume of hardenable material, and at least oneplug configured to lead or follow the volume of hardenable material thatis pumped through a tubular, the plug has one or more portions made of amaterial configured to weaken in response to being exposed to anactivation fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 depicts a cross sectional view of a removable plug arrangementdisclosed herein;

FIG. 2 depicts a partial cross sectional view of an alternate removableplug arrangement disclosed herein in a first position;

FIG. 3 depicts a cross sectional view of the alternate removable plugarrangement of FIG. 2 in a second position;

FIG. 4 depicts a cross sectional view of the alternate removable plugarrangement of FIG. 2 in a third position; and

FIG. 5 depicts a partial cross sectional view of the alternate removableplug arrangement of FIG. 2.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Referring to FIG. 1, an embodiment of a removable plug arrangement isillustrated at 10. The arrangement 10 includes a single plug 14A or 14B,although alternate embodiments can include more than one of the plugs 14as will be disclosed with reference to additional Figures herein. Theplug 14 can be used to lead or to follow a hardenable material 18,illustrated herein as cement, being pumped through a tubular 22 such asa casing, liner or drill string, for example. The plug 14 in theillustrated embodiment is shown following cement 18. The plug 14includes a portion 26, shown as a core of the plug 14 that is made of amaterial configured to weaken when exposed to an activation fluid. Theplug 14 also includes a seal 30, made of a flexible material, such as anelastomer, for example, to allow the seal 30 to deformingly sealinglyengage with walls 36 of the tubular 22 while moving therethrough.

The foregoing arrangement 10 allows an operator to clear the tubular 22of cement 18 when finishing the pumping of the cement 18. This isaccomplished by pumping the plug 14 following the cement 18, through thetubular 22 while sealing the plug 14 to the walls 36. The cement 18remains separated from displacement fluid 40 on an opposing side of theplug 14 by the plug 14 itself. This separation prevents dilution andcontamination of the cement 18 during the pumping operation. The plug 14can be configured to engage with a landing device 44 (see FIG. 2) suchas a landing collar, for example, positioned at a selected locationwithin the tubular 22. An activation fluid, which causes dissolution ofthe portion 26, can then be pumped to expose the portion 26 of the plug14 thereto to weaken the portion 26 thereby facilitating its removal viaa drilling or milling process, for example. The weakening of the portion26 prior to removal of the plug 14 can simplify and expedite the processand lessen chances of generating undesirable contamination from residualparts of the plug 14 residing within the tubular 22. The portion 26 maybe configured to weaken significantly after being exposed to theactivation fluid in about a few hours to about a few days. Additionally,the weakening can include substantially dissolving the portion 26.

Some embodiments of the arrangement 10, include a bore 52 formed throughthe seal 30 to assure the portion 26 is exposed to the activation fluid.Without the bore 52, activation fluid would be prevented from cominginto direct contact with the portion 26 when pumped thereagainst due tothe seal 30 blocking such exposure. The bore 52 can extend a significantdepth into the portion 26 to increase surface area of the portion 26that is exposable to the activation fluid to increase a rate ofdissolution of the portion 26 and to cause more uniform weakening of theportion 26. Alternatively, the bore 52 could be post-drilled into theplug 14 only at such time exposure to the activation fluid is desired.It should also be noted that activation fluid could be employed as thedisplacement fluid 40 with either alternative of the plug 14 (i.e.pre-bored or post-drilled). In the case wherein the plug 14 ispre-bored, exposure of the portion 26 begins as soon as thedisplacement/activation fluid 40 begins urging the plug 14 through thetubular 22. Consequently, the weakening of the portion 26 is timed(based on the chemical make-up of the portion and thedisplacement/activation fluid 40) to prevent over-weakening of theportion 26 until the cementing operation has been completed.

In some embodiments of the removable plug arrangement the portion 26 ismanufactured from a high strength controlled electrolytic metallicmaterial and is degradable in response to exposure to an activationfluid such as brine, acid, an aqueous fluid or combinations of one ormore of these. A variety of suitable materials and their methods ofmanufacture are described in United States Patent Publication No.2011/0135953 (Xu et al.), that is hereby incorporated by reference inits entirety.

Referring to FIGS. 2-4, an alternate embodiment of a removable plugarrangement is illustrated at 110. The arrangement 110 includes two ofthe plugs 14, designated in this embodiment as 14A and 14B. Additionallythe arrangement 110 includes two plugs 114A and 114B that are sealinglyreceptive to the two plugs 14A and 14B respectively in a nestingarrangement. The plugs 114A and 114B have a port 116 that is sealinglyreceptive to the plugs 14A and 14B. It is also possible for a cementingoperation to employ just one each of 14A or 14B and 114A or 114B. Insuch a system the pair of the plugs 14A and 114A or 14B and 114B may beemployed to follow the cement 18 to thereby maintain separation of thedisplacement fluid 40 from the cement 18. Determination of which of theplugs 14A, 14B, 114A, 114B to use depends upon the specifics of theoperation.

The nesting of the plugs 14A and 14B into the plugs 114A and 114B allowan operator to maintain separation of the cement 18 from thedisplacement fluid 40 with one of the plugs 14A, 14B while pumpingthrough a smaller diameter tubular, and then to continue maintainingseparation of the cement 18 from the displacement fluid 40 while pumpingthe nested plugs 14A, 14B, 114A, 114B through a larger diameter tubular.To do so an operator positions the plug 114A, for example, in the largertubular downstream of a smaller tubular through which the plug 14A isfirst pumped. The plug 114A is initially open to flow through the bore52. When the plug 14A engages with the plug 114A it seals the bore 52thereby preventing additional flow therethrough. As such, the pair ofplugs 14A with 114A or 14B with 114B can be used to lead or to followthe cement 18.

In FIG. 2 the pair of plugs 14A and 114A have been pumped ahead of thecement 18 and have landed on a landing collar 44 positioned within atubular 124. The landing collar 44 forms an annular flow path 128 thatallows the cement 18 to flow past the plugs 14A and 114A seated thereatto allow the cementing process to continue as is illustrated in FIG. 3.In FIG. 4 the second set of plugs 14B and 114B have landed at the firstpair of plugs 14A and 114A with the displacement fluid 40 positionedupstream thereof. This designates the end of the cementing operation.

Referring to FIG. 5, the two plugs 114A and 114B are shown without theplugs 14A and 14B positioned within the port 116 for purposes ofsimplicity. Each of the plugs 114A and 114B are made of seals 130A, 130Band portions 126A, 126B, respectively. Similar to the seal 30, the seals130A, 130B are made of a flexible material, such as an elastomer, forexample, to allow the seals 130A, 130B to deformingly sealingly engagewith walls of the tubular 124 while moving therethrough. The portions126A, 126B are made of one or more parts that are (similar to theportion 26) in that they are configured to weaken when exposed toactivation fluid. The parts that make up the portions 126A, 126B canvary as is shown by the variation in parts that make up the portion 126Aof the plug 114A compared to the parts that make up the portion 126B ofthe plug 114B. The portion 126A includes a nose 132, a body plug 134, abottom insert 138, a bottom sleeve 142, a bottom collet 146, a connector150 and a slip 154. The portion 126B includes a retaining collet 158, abody plug 162, a top insert 166, a top sleeve 170 and a top collet 174.In this embodiment, all of the parts that make up the portions 126A and126B are made of a weakenable material such as that described above. Theplugs 114A, 114B are configured such that all of the parts that definethe portions 126A, 126B are exposed to activation fluid once activationfluid is positioned within the ports 116. As such, weakening of allparts of the portions 126A, 126B is initiated substantiallysimultaneously.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. Also, in the drawings and the description, there have beendisclosed exemplary embodiments of the invention and, although specificterms may have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited. Moreover, theuse of the terms first, second, etc. do not denote any order orimportance, but rather the terms first, second, etc. are used todistinguish one element from another. Furthermore, the use of the termsa, an, etc. do not denote a limitation of quantity, but rather denotethe presence of at least one of the referenced item.

What is claimed is:
 1. A removable plug arrangement comprising at leastone plug configured to lead or follow a hardenable material being pumpedthrough a tubular, the plug having one or more portions made of amaterial configured to weaken when exposed to an activation fluid. 2.The removable plug arrangement of claim 1, wherein the material is acontrolled electrolytic metallic material.
 3. The removable plugarrangement of claim 1, wherein the at least one plug also includes aseal configured to flexibly sealingly engage walls of the tubular whilemoving therethrough.
 4. The removable plug arrangement of claim 1,wherein the at least one plug includes a plurality of plugs.
 5. Theremovable plug arrangement of claim 4, wherein the plurality of plugsincludes at least one plug leading the hardenable material and at leastone plug following the cement.
 6. The removable plug arrangement ofclaim 5, wherein the at least one plug leading the hardenable materialincludes two plugs, a first of the two plugs being sealingly attachableto plug a port through a second of the two plugs when engaged therewith.7. The removable plug arrangement of claim 6, wherein the second of thetwo plugs is sized and configured to sealingly engage walls of a tubularhaving a larger diameter than a tubular that the first of the two plugsis sized and configured to sealingly engage walls of.
 8. The removableplug arrangement of claim 5, wherein the at least one plug following thehardenable material includes two plugs, a first of the two plugs beingsealingly attachable to plug a port through a second of the two plugswhen engaged therewith.
 9. The removable plug arrangement of claim 8,wherein the second of the two plugs is sized and configured to sealinglyengage walls of a tubular having a larger diameter than a tubular thatthe first of the two plugs is sized and configured to sealingly engagewalls of.
 10. The removable plug arrangement of claim 1, wherein the atleast weakening of the one or more portions includes substantiallydissolving the one or more portions.
 11. The removable plug arrangementof claim 1, wherein the at least one plug has at least one boreconfigured to facilitate expose or portions of the one or more portionsto the activation fluid.
 12. The removable plug arrangement of claim 1,wherein the material is configured to weaken significantly afterexposure to the activation fluid in about a few hours to about a fewdays.
 13. The removable plug arrangement of claim 1, wherein thehardenable material is cement.
 14. A method of removing a plugarrangement comprising: exposing one or more portions of at least onecementing plug to an activation fluid capable of weakening the one ormore portions; weakening the one or more portions; and drilling ormilling through the weakened one or more portions.
 15. The method ofremoving a plug arrangement of claim 14, further comprising dissolvingthe one or more portions with the activation fluid.
 16. A removable plugarrangement comprising: a volume of hardenable material; and at leastone plug configured to lead or follow the volume of hardenable materialbeing pumped through a tubular, the plug having one or more portionsmade of a material configured to weaken in response to being exposed toan activation fluid.